The present invention relates to a technique of editing a multimedia title which comprises various sources such as motion pictures, still pictures, text data, background still image, graphics, and a scenario describing the source list, presentation method and characteristics of the sources into video signals. It also relates to a technique of coding a type of sequential video signals into coded video signals such as MPEG responsive to a type of data.
In this specification, the technical terms used in the above paragraph are defined as follows:
xe2x80x9csourcexe2x80x9d : a displayed unit of respective types of information such as motion pictures, still pictures, text data, background still image, graphics, and the like
xe2x80x9cscenarioxe2x80x9d : a method of displaying a source, e.g. a timing and a location in a screen of a source to be output
xe2x80x9cmultimedia titlexe2x80x9d : data comprising sources and their scenarios
xe2x80x9cdata typexe2x80x9d : characteristics of a source, such as a type of information, picture quality, application, and process provided
In recent years awareness of multimedia has increased in the market, and video-on-demand-systems have drawn consumers"" attention because this system can provide users with moving pictures on a television set or a personal computer anytime when the users want to watch them.
In the video-on-demand-system, a video comprising various data such as motion pictures, still pictures, text data and the like is presented as a multimedia title so that an efficient presentation can be achieved. Therefore, the market has demanded a multimedia-on-demand-system that delivers multimedia titles responsive to requests from respective terminals, which then reproduce the titles.
The following two methods are available for reproducing the multimedia title.
(1) The reproduction terminal relevantly reproduces, decodes and edits respective sources following their scenarios, and then displays them at a specified time in a specified region so that a plurality of videos can be edited on a screen.
(2) The terminal reproduces respective sources based on information from their scenarios by using reproducing methods relevant to each source, and edits them on a screen.
According to the methods discussed above, the terminal must display respective sources in accordance with their characteristics e.g. text data is developed into fonts. In the case of multimedia title including motion pictures, the terminal must have versatile functions such as displaying motion pictures, still pictures and text data. As such, reproduction of the multimedia title demands a lot of functions of the terminal, thus reducing processes in the terminal is needed.
A technique for reducing a number of functions in the terminal is disclosed in the Japanese Patent Application Non-examined Publication No. H06-301495. It teaches that if the terminal has no character-font-information, the data to be input to the terminal can be equipped with some character fonts responding to characters used in a content of a presentation so that the characters can be reproduced. However, this method does not contribute to reduce a lot of functions in the terminal.
Another method is that a combination of e.g. a scan converter with a hard encoder converts the multimedia title into coded video signals. Most of the scan converters only accept sources converted into analog-signals, and this conversion deteriorates picture quality. The hard encoder does not provide an optimal coding to the sources such as still pictures and text data which can predict the next frame, but provide the same coding as other sources such as motion pictures. Unnecessary coding is thus provided, which lowers picture quality and demands a lot of calculation. The hard encoder also provides the same weighing as other sources ▭ natural images including motion and still picture ▭ to text data, graphics or monotonous artificial images. These artificial images are painted with less numbers of colors and can be used in background. Then the weighted data are quantized, and thus picture quality is lowered.
The present invention addresses the problems discussed above and aims to achieve the following targets.
(1) Realize a low cost reproduction terminal by editing a multimedia title into a type of video signals so that a necessary process for the terminal is only a reproduction of motion pictures.
(2) Code the edited video signals so that the following objectives can be realized: 2-1. Improving picture quality, 2-2. Reducing a number of calculations, and 2-3. Improving a coding rate.
In order to achieve the goals discussed above, the present invention edits a multimedia title into a type of video signals such as motion pictures. The multimedia title comprises various sources including motion pictures, still pictures, text data, background still pictures, and the like as well as scenarios including the source list, methods of presentation and characteristics of the sources.
The present invention then codes the edited video signals into coded video signals such as MPEG. When coding, the present invention utilizes the scenarios, and thereby assigning relevant coding methods to respective sources based on a ratio of region areas where respective data types appear. As a result, respective sources can be coded in accordance with their data types.
In other words, a multimedia title comprising various kinds of sources and their scenarios is converted into a type of coded video and audio signals following some format such as MPEG. The reproduction terminal thus can be equipped with only a function decoding and reproducing the type of coded video and audio signals.
When converting the edited video signals into the coded video signals such as MPEG, the scenarios contribute to code the signals in a suitable manner for the characteristics of the multimedia title such as kinds of sources, ratios of respective sources making up the title. In this case, the scenarios also contribute to code the signals relevant to data types of respective sources responsive to the regions where different data types are displayed. As a result, coding rate is increased, a number of calculations are decreased, and picture quality is improved because the coding method accommodates respective data types such as text data.